A large number of plastics are often used in any field in the world currently. Plastics are expected to replace metal as materials in more fields also in the future. In addition, brand marks, maker marks, various patterns, etc. are indicated in most of plastic products including IC apparatus such as cellular phones, personal computers, TV sets and digital cameras, household products such as eating utensils and stationery products, and the like. Particularly, indication marks using a printing method or a plating method are preferred because there is no feeling of mismatching with bodies, differently from attached labels or the like.
Particularly, indication marks, patterns, etc. using metal plating of gold, silver or the like, can provide a sense of luxury together with a feeling of graceful depth so as to improve the values of products. Such indication marks, patterns, etc. can be regarded as youth orientation.
It is, however, difficult to electroplate plastic with metal. A special conductive plastic material such as polyacethylene using AsF5 or the like as dopant may be used as a material instead of metal. Alternatively, a vapor deposition method may be used, or an electroless plating method or the like may be used. However, the material is restricted because heat not lower than 80° C. is applied to the material. At any rate, it has been inevitable to depend on an expensive and complicated technique.
In addition, most products are often arranged by a combination of curved surfaces due to aesthetic sense. It is not always impossible to perform plating upon these surfaces, but a considerably complicated and advanced technique is required technically. Thus, the products have been expensive due to their manufacturing cost. In addition, there has been a tendency that the outline of an obtained indication mark or pattern is not always clear.
Further, in applications to casings of computer apparatuses, electronic image display screens, etc., not only is it expected to display beautiful indication marks or images but it is also often expected to provide an effect of shielding required portions from electromagnetic waves. In the background art, electromagnetic wave shielding means are often implemented by means of covering the whole of the casing with an electromagnetic wave shielding material in a vapor deposition method or the like. The means has been regarded as unsatisfactory in regard to the cost.
In addition, direct drawing with an electron beam has been used in microscopic electric circuits such as IC devices in recent years. Further, a method in which an electric circuit is arranged directly out of conductive printing ink has been also investigated. The content of conductive powder to provide conductivity, for example, the content of Ag powder has to satisfy not only the condition that it should provide a function of having good conductivity as an essential function but also the condition that it must not give any damage to the printing characteristic as printing ink. These two conditions are, however, contrary to each other.
In order not to spoil this printing characteristic, the content of the conductive powder is limited up to 20-30%. This does not always satisfy the condition for obtaining good conductivity. In addition, when the printed line width is shorter than 10 μm, the absolute value of power particle density itself becomes too small to expect good conductivity. Therefore, an electric circuit having good conductivity by a printing method has been desired strongly.
As described above, it is strongly requested to attach various indication marks, images, etc. by plating or the like comparatively inexpensively on the surface of a product to be printed or coated by use of a printing method. In addition, a means for providing an electromagnetic wave shielding effect in a required portion inexpensively is also highly requested. Further, it is strongly desired to produce a microscopic electric circuit having good conductivity by use of a printing method desired in regard to cost.
In consideration of the aforementioned requests, an object of the present invention is to provide plating of an image or the like or a microscopic electric circuit surely and inexpensively on the surface of a product to be printed or coated by use of a printing method. In addition, another object of the invention is to provide a means for applying an electromagnetic wave shielding effect to a required portion comparatively inexpensively.